A need presently exists for an inexpensive, non-intrusive means of monitoring power consumption by end use, in an industrial or commercial building. Measurement of peak electrical demand for lighting, heating, cooling and air distribution in a building is useful for both research and billing purposes.
As early as 1953, as disclosed in U.S. Pat. No. 2,654,068 issued to Mertens, entitled "Combined Fuse and Demand Meter," demand (current) meters were disposed in a housed fuse construction, and mounted on the door thereof. Those prior systems, however, provided an indicator only; no provision was made for recording or analyzing data either concurrently or subsequently, nor was an end use application anticipated.
A non-intrusive load monitoring system has been developed for monitoring appliances in private residences, as illustrated and described in U.S. Pat. No. 4,858,141 issued to Hart et al, on Aug. 15, 1989, entitled "Non-intrusive Appliance Monitor Apparatus." The above-mentioned system utilizes harmonics to sense individual devices within a residence from the main meter. This system is generally expensive, despite the fact that it attempts to reduce cost by using sophisticated software in lieu of hardware.
One of the major drawbacks of this prior system is its inability to work effectively with multi-state or variable speed devices, albeit it was never designed to do so. The operational dependence of the aforementioned system upon individual device characteristics makes it impractical for monitoring commercial structures. This is so because commercial buildings have a wider variety of devices, which would require site specific customization. The cost alone of surveying a building for such customization would be prohibitively high. Also, the building industry is currently attempting to eliminate devices that result in disturbances through the electrical system. This would eliminate the ability of the aforesaid system to detect many of the power consuming units.
The present invention seeks to provide an inexpensive, non-intrusive system for monitoring power consumption by end use rather than by identifying a particular device. The invention is incorporated in the circuit breaker panels of commercial buildings, either by retrofit or as original equipment. Of course, economies of installation are achieved by incorporating power measurement into an existing building component (i.e., the circuit breaker), when possible, rather than designing a system having new components which must be interfaced with existing building systems.
The power consumed in any circuit is dedicated to a particular end function, such as lighting or cooling, etc. The measurement of any particular power drain is transmitted to a multiple end use register, where it is summed with similar measurements from other end use sources. Power consumption measurement can be integrated to provide both kW and kW/hr use.